These tolerances are specified in terms of a tolerance zone, which is a defined area or volume within which the feature must lie.
The "h" class defines the permissible deviations for the shape and orientation of a part, such as how flat a surface must be or how perpendicular two edges are . iso 2768-mh tolerance chart
Angular tolerances (when not otherwise specified), typical values for grade m: These tolerances are specified in terms of a
These apply to linear dimensions like external sizes, internal sizes, and step heights. Nominal Size Range (mm) Tolerance (± mm) > 30 to 120 > 120 to 400 > 400 to 1000 > 1000 to 2000 > 2000 to 4000 Data sourced from Dau Components Part 2: Geometrical Tolerances (H - Fine) Nominal Size Range (mm) Tolerance (± mm) >
The standard is divided into two parts to simplify engineering drawings by removing the need for individual tolerance callouts on every single feature.
ISO 2768‑2 provides default values for geometrical tolerances when such symbols are omitted, but it is safer to specify geometric controls directly when required.